It can work. Banyuls is a famous sweet wine match for chocolate. I have had rich Cabernets that did OK. Even vintage Port...

But I don't think it is a "natural" match. Even when it's good it's a little bit of a stretch. On the other hand, COFFEE!

We were so frustrated, especially in England, where the waitress would watch with an eagle eye, and when you ate the LAST DAMN BITE of your chocolate dessert, she would briskly bring you the coffee you had ordered -- which we ordered TO GO WITH DESSERT. Not an uncommon experience in Europe.